As a general rule, portable devices, such as radiotelephones and computers, continue to shrink in size and to be configured in small compact packages (i.e., "pocket" sized radiotelephones). Recent radiotelephones have incorporated a variety of new features ranging from optional communication services, including Internet access, through videogames. As a result, menu structures of such devices typically become more complex. Such communication device applications, as well as devices such as laptop computers and portable games, may utilize multi-directional switches, such as 4-way switches. A select switch may be provided apart from, or integrated with, the pressure sensitive switch.
Various known approaches to pointing devices include a joystick, a mouse and a trackball. A mouse and a trackball typically use electromechanical or optical systems to convert a rotational motion of a ball to a linear motion of a cursor. Joysticks typically include an array of digital contact switches that detect when the joystick is moved in a particular direction. Various pointing devices detect both direction and pressure by sensing the magnitude and direction of a force applied to the pointing device. Examples of pressure sensitive pointing devices are described in U.S. Pat. Nos. 5,231,386 ("the '386 patent") and U.S. Pat. No. 5,828,363 ("the '363 patent").
The '386 patent is directed to a keyswitch-integrated pointing assembly in which a plurality of substantially planar force sensing elements are disposed on a planar surface adjacent a keyswitch on a keyboard. The device thus combines a keyswitch with force sensing resistor elements. A rubber dome sheet extends between the actuator element and the force sensing elements to disperse applied forces smoothly. The forcing sensing resistors are pre-loaded to bias the elements into a substantially linear operating region when no force is applied to address problems with stability associated with non-linear operating ranges of force sensing resistors.
The '363 patent is directed to another type of force-sensing pointing device utilizing force sensing resistors to detect the magnitude and position of an applied force. A connector, such as an elastomeric adhesive, maintains a force transfer member in contact with the force sensing resistors. A related product is available from Interlink Electronics of Camarillo, Calif. as described in the associated High-Precision MicroJoystick Integration Guide. This product is described as being suited to computer-cursor control and as providing both a click (select switch) function and cursor speed control responsive to the amount of an applied pressure.